1. Field of the Invention
The present invention relates generally to apparatus and methods for removing entrained gas from liquids, and more particularly to an apparatus and method for removing entrained gas from drilling mud.
2. Description of the Prior Art
During the drilling of oil and gas wells, gas bearing zones are often encountered. When the pressure head of the mud column is less than the pressure of the gas in a particular formation, gas will migrate into and become entrained in the mud. The presence of entrained gas decreases the density of the mud. If the gas cut mud is pumped back into the well, the mud column will weigh less, which will allow even more gas to become entrained, thereby further lowering the density of the mud. If entrained gas is not removed from the mud prior to its being pumped back into the well, a kick or blow out may result.
The prior art has provided numerous methods and apparatus for removing entrained gas from drilling mud. Such apparatus and methods typically employ one or a combination of four distinct separation mechanisms, which include centrifugal separation, impingement of the mud against a barrier to break out gas bubbles, thin film flow to increase surface area, and vacuum separation.
Certain apparatus and methods of the prior art employ more than one of the four primary separation mechanisms; however, none of the such apparatus and methods employ all of the primary separations mechanisms. Moreover, none of the apparatus and methods of the prior art are effective to remove more than about 85%-90% of the entrained gas in drilling mud.
It is therefore an object of the present invention to provide an improved method and apparatus for degassing drilling mud. It is a further object of the present invention to provide a method and apparatus that combines all of the primary separation mechanism.